[xblueh2o]

Searched through the old threads and found this one which answered one of my questions. It was regarding what to do about the first couple of holes in the skin closest to the spar but I have another one for those of you who have built a Showplanes FB. In laying out the line today I just made a quick pen line on the plastic. Measuring up from the bottom of the stock skin along the leading edge to the new 175? line. It looks like I will be taking off essentially one inch right at the nose. For those of you who have done the mod before does that sound right? I would hate to screw up a skin. I hadn't thought about having to make a new nose rib. Simple enough to do, just hadn't thought of that.

 

[Dave Stephens]

From memory that sounds about right, I think I did slightly less then ground a bit of of the skin and rib flange (prob less than 1/8")

not the best pic, but you can just see it

 

[xblueh2o]

Thanks Dave.
Just making sure I am in the ballpark. Would hate to ruin a skin. At least I get to (maybe) build a new rib. Haven't done that in a while.

Thanks again.

 

[xblueh2o]

Wow, has it really been nearly a month since I was able to work on my plane? Staring to seriously consider QB. Anyway...
I asked Bryan at Showplanes the same question and he agreed that about an inch was expected to be removed at the nose but he noted that I had begun the line in the wrong place. I had started mid spar. Bryan said to begin at the forward edge. So today I laid out the line again and came across an edge distance conundrum. I marked roughly where the new holes would be then checked edge distances and found the first hole to be acceptable. The distance from the new third hole to the remainder of the stock third hole was also acceptable. The problem child is the second hole. There is insufficient edge distance between the new second hole and the stock second hole. As you can see on the opposite side flange I really can't move the new hole vertically enough without running into to the radius of the web to flange interface to get edge distance to the stock hole. Using the stock hole is out for just plain insufficient edge distance to the flange edge so moving it vertically is not a viable option. I could move the hole horizontally but this brings up more questions.
If I move only the second hole I end up with a one off uneven rivet spacing. Do I move it forward or aft?
If I change the rivet spacing to accommodate edge distance to the stock second hole, should I increase or decrease the spacing?
Local builder suggested putting a flush rivet in the stock hole and then drilling/riveting the second hole in current location. Not sure if that would work with regards to two holes so closely spaced being dimpled.
So many questions. Opinions?

 

[Scott Hersha]

I had a line drawn similar to what I see in your drawing, but maybe a little higher. I just bent the nose rib up and out of the way, made the cut with a cut off wheel, bent the rib back down into place (the rivets in the forward spar stayed), back drilled with an angle drill through the holes in the rib and then riveted it in place - after dimpling the skin. I had to bend the rib flanges out slightly to make them lay flat against the skin in their new location, but not much. I think I cut off more than an inch - maybe close to two. Your tail fairing will cover this easily. I have at least 1/2 inch between the bottom of the nose of the VS and the turtle deck skin.

 

[DanH]

Like Scott said....raise the cut angle higher, cut, drill, and rivet. You're in more danger of not cutting enough than too much.

 

[xblueh2o]

Yep, Bryan agreed that moving the line slightly was the best plan. I will probably increase the angle slightly to get edge distance on hole 2 while retaining edge distance on hole 1.
Thanks all for the input.

 

[Tailpilot]

Started line aft of flange

I'm sure I'm late on this. Looking at the diagram from showplanes it looks like the line is started from the aft part of the flange. Doing it this way seems avoid any edge distance problems

 

[Tom Martin]

Just leave that rib out until you go to fit it to the airplane. Then you can cut it as much as is required. The glass faring goes 2 to 4" up the stab, depending on how you do it, and that gives you a big margin here. The rest of the stab can be completed and closed at this time, just leave that little rib, and rivets out at this time.

 

[xblueh2o]

The picture in post #8 is pretty much dead on what I ended up with. I began the line at the aft edge of the spar per the drawing.
This five minutes I have the cut made, the skin's edges are dressed and ready. I played with the stock rib to see if I could re-use it but decided to make a new rib. I have the pattern made and I made a proof of concept rib to check fit out of some unknown aluminum alloy that was available at the local hardware store. Now I am just waiting for some sheets of the correct alloy to show up and I will be back in business. Been very busy with work recently so my time on the project has been limited.

Question for those that made a new rib. Here is my plan, let me know if you see a problem. Place the new un-drilled rib in position under the un-drilled skin. Match drill through the skin into the rib the first hole (the only remaining original hole in the skin). Measure to assure edge distance on the second partially remaining hole for the new hole, drill new hole in skin and rib. Remove the rib, mark and drill the remaining holes in the rib making sure to keep edge distances. Re-install rib, back drill the skin using the rib as the template. The theory for the procedure is to make 100% sure I have any required distances on the rib for old holes, new holes ends, edges etc etc etc.

Thanks again to all for your input.